Differential Space-time Modulation Scheme Research Articles

Adaptive Coherent/Non-Coherent Single/Multiple-Antenna Aided Channel Coded Ground-to-Air Aeronautical Communication

In this treatise, first of all, we conceive a generic multiple-symbol differential sphere detection (MSDSD) solution for both single- and multiple-antenna-based noncoherent schemes in both uncoded and coded scenarios, where the high-mobility aeronautical Ricean fading features are taken into account. The bespoke design is the first MSDSD solution in the open literature that is applicable to the generic differential space-time modulation (DSTM) for transmission over Ricean fading. In the light of this development, the recently developed differential spatial modulation and its diversity counterpart of differential space-time block coding using index shift keying are specifically recommended for aeronautical applications owing to their low-complexity single-RF and finite-cardinality features. Moreover, we further devise a noncoherent decision-feedback differential detection and a channel-state information estimation aided coherent detection, which also take into account the same Ricean features. Finally, the advantages of the proposed techniques in different scenarios lead us to propose for the aeronautical systems to adaptively: 1) switch between coherent and non-coherent schemes; 2) switch between single- and multiple-antenna-based schemes as well as; and 3) switch between high-diversity and high-throughput DSTM schemes.

Single-RF Index Shift Keying Aided Differential Space–Time Block Coding

We propose a new single-RF differential space–time block coding using index shift keying (DSTBC-ISK), which is the first differential space–time modulation (DSTM) scheme that can simultaneously achieve the following three imperative objectives: First, forming a finite-cardinality transmit-signals set; second, retaining a single-stream maximum-likelihood (ML) detection complexity; and third, offering a beneficial transmit diversity gain. In order to make a fair comparison, we also conceive a low-complexity single-stream detector for DSM. Furthermore, in order to improve the performance of finite-cardinality DSTM schemes at higher throughputs, we propose to generalize both differential amplitude shift keying (DASK) and amplitude shift keying (ASK), which subsume the existing two-/four-level-ring star quadratic–amplitude modulation (QAM) solutions as special cases. As a result of using star QAM signaling, the power of the DSTM's signal matrix becomes variable. Against this background, we further develop bespoke ML, minimum mean squared error, and least-square detectors for DSTM using DASK/ASK. Our simulation results demonstrate that the proposed DSTBC-ISK is capable of achieving substantial diversity gains over DSM without eroding its low transceiver complexity.

Differential Modulation Exploiting the Spatial–Temporal Correlation of Wireless Channels With Moving Antenna Array

Provisioning reliable wireless services for railway passengers is becoming an increasingly critical problem to be addressed with the fast development of high speed trains (HST). In this paper, exploiting the linear mobility inherent to the HST communication scenario, we discover a new type of spatial-temporal correlation between the base station and moving antenna array on the roof top of the train. Capitalizing on the new spatial-temporal correlation structure and properties, an improved differential space-time modulation (DSTM) scheme is proposed. Analytical expressions are obtained for the pairwise error probability of the system. It is demonstrated that, the proposed approach achieves superior error performance compared with the conventional DSTM scheme. In addition, an adaptive method which dynamically adjusts the transmission block length is proposed to further enhance the system performance. Numerical results are provided to verify the performance of the proposed schemes.

Unitary Differential Space–Time Modulation With Joint Modulation

We develop two new designs of unitary differential space-time modulation (DSTM) with a low decoding complexity. Their decoder can be separated into a few parallel decoders, each of which having a decoding search space of less than radicN if the DSTM codebook contains N codewords. Both designs are based on the concept of joint modulation, which means that several information symbols are jointly modulated, unlike the conventional symbol-by-symbol modulation. The first design is based on an orthogonal space-time block code (O-STBC) with joint constellation constructed from spherical codes. The second design is based on a quasi-orthogonal STBC (QO-STBC) with specially designed pairwise constellation sets. Both the proposed unitary DSTM schemes have a considerably lower decoding complexity than many prior DSTM schemes, including those based on group codes and Symplectic group Sp(2), which generally have a decoding search space of N for a codebook size of N codewords and a much better decoding performance than the existing O-STBC DSTM scheme. Between the two designs, the proposed DSTM based on the O-STBC generally has a better decoding performance, whereas the proposed DSTM based on the QO-STBC has a lower decoding complexity for eight transmit antennas.

A novel linear Differential Space-Time Modulation

Based on the Complex Orthogonal Linear Dispersion (COLD) code, a novel linear Differential Space-Time Modulation (DSTM) design is proposed in this paper. Compared with the existing nonlinear DSTM schemes based on group codes, the proposed linear DSTM scheme is easier to design, enjoys full diversity and allows for a simplified differential receiver, which can detect the transmitted symbols separately. Furthermore, compared with the existing linear DSTM based on orthogonal design, our new construction can be applied to any number of transmit antennas. Similar to other algorithms, the proposed scheme also can be demodulated with or without channel estimates at the receiver, but the performance degrades approximately by 3dB when estimates are not available.

A Differential Space–Time Modulation Scheme for Correlated Rayleigh Fading Channels: Performance Analysis and Design

Differential space-time modulation (DSTM) is an encoding technique for multiantenna systems that allows the receiver to detect the transmitted signals without the knowledge of the fading channels. It can be viewed as an extension of the differential phase-shift keying scheme in single antenna systems. In this paper, we investigate the performance of multiantenna systems employing DSTM under spatially correlated Rayleigh fading channels. We present three expressions for calculating the pairwise error probability (PEP) of the DSTM scheme. The first expression allows us to numerically calculate the exact PEP. The remaining two are closed-form expressions of the exact PEP at asymptotically high signal-to-noise ratios and the PEP upper bound. It is found that when the distance matrix is proportional to the identity matrix, the error probability is determined by the channel correlation matrix and the initial transmitted code matrix. Based on the new PEP upper bound, we derive a criterion for optimizing the initial code matrix for this special case. Simulation results show that the performance of the differential space-time coded systems can be significantly improved by designing the initial transmitted code matrix according to the proposed design criterion

Single-symbol-decodable differential space-time modulation based on QO-STBC

We present a novel differential space-time modulation (DSTM) scheme that is single-symbol decodable and can provide full transmit diversity. It is the first known singlesymbol- decodable DSTM scheme not based on Orthogonal STBC (O-STBC), and it is constructed based on the recently proposed Minimum-Decoding-Complexity Quasi-Orthogonal Space-Time Block Code (MDC-QOSTBC). We derive the code design criteria and present systematic methodology to find the solution sets. The proposed DSTM scheme can provide higher code rate than DSTM schemes based on O-STBC. Its decoding complexity is also considerably lower than DSTM schemes based on Sp(2) and double-symbol-decodable QOSTBC, with negligible or slight trade-off in decoding error probability performance.

Closed-form blind MIMO channel estimation for orthogonal space-time block codes

In this paper, a new computationally simple approach to blind decoding of orthogonal space-time block codes (OSTBCs) is proposed. Using specific properties of OSTBCs, the authors' approach estimates the channel matrix in a closed form and in a fully blind fashion. This channel estimate is then used in the maximum-likelihood (ML) receiver to decode the information symbols. The proposed estimation technique provides consistent channel estimates, and, as a result, the performance of the authors' blind ML receiver approaches that of the coherent ML receiver, which exploits the exact channel state information (CSI). Simulation results demonstrate the performance improvements achieved by the proposed blind decoding algorithm relative to the popular differential space-time modulation scheme.